Bryant 90+ Intermittant Surface Ignitor

[j.gearhart]

Bryant 90+ Model 350MAV installed in Feburary 2001. Furnace has worked fine until November 2007 when this intermittant problem started. When the thermostat calls for heat the inducer motor starts and runs. The surface ignitir intermittantly will not come on. I can watch through the window into the combustion chamber and sometimes the ignitor will start to come on and them go off. This can happen several times before it comes on long enough for the gas valve to open and the the furnace will run. The local Bryant dealer has replaced the PCB and hot surface ignitor. The problem is very intermittant but the service people have seen the problem. One time the inducer motor ran for 40 minutes befor the surface ignitor stayed on long enough for the gas valve to open. (nerer get any error code) You can hear the ignitor relay drop out when the ignitor shuts off prematurely. Checked all AC connections and thermostat connections. The dealer has questioned the thermostat but the problem only happens during the start cycle and the inducer motor never changes speed or pitch when the ignitor fails. Once the gas valve opens the furnace runs AOK until the thermostat is satisfied. Any suggestions !!!!